The Count
Big Mama was the brown monster with pointy ears and a very large mouth. Debuted in the Don Knotts episode, also appeared in the "Ugly" number with the other monsters, a couple of spots in the Rich Little episode (as well as the goodnights of this episode and the Zero Mostel episode), he ate John Cleese's agent and ate Miss Piggy in the Carol Burnett episode. The name Big Mama, though, was never actually used on the show or in anything else the monster appeared in (for that matter, neither was DogLion Beast).
DogLion, to my eyes at least, is kind of grayish, shaggy, has a rectangular head and dark grey horns and a more or less black face. He debuted in the Madeline Kahn episode, appeared in the animal shelter sketch with Dom DeLuise (along with Big Mama), the closing number on the Cloris Leachman episode, he did "Beauty and the Beast" with Lesley Ann Warren, was in the number "He's the Greatest Dancer" with Lola Falana, and assisted Doug Henning in his final illusion on his episode.
The rest of the questions have been answered, though I wouldn't call the Snowths aliens. They're just creatures.
David "Gorgon Heap" Ebersole